Web Interface Command Filter on Group Member

So I am trying to see if it is possible to only show a custom group command to a user only if that user is NOT a member. I am aware of the AVFilter in the <IsCommandAllowedFilter> tag, but that seems like it only takes hard-coded strings, in which my case would need to be more "dynamic" since it would vary by if if the current user is a member of this group.

Is this possible to do in ARS? I was thinking maaaaybe I could leverage the 'IsCommandAvailable.vbs' script but I am not sure how to pass the current user's information and that group they are viewing to it to return if they are a member.

Any feedback/suggestions would be most appreciated. Thanks.